Role of Silica-Epoxy Interface and Deep Traps on the Dielectric Breakdown Performance of Epoxy Moulding Compounds (EMC)

Abstract

In this paper, the properties of silica-epoxy interface and effect of deep traps on the dielectric breakdown performance of Epoxy Moulding Compounds (EMC) were investigated to address the lack of understanding on how the higher voltages and frequencies, affect the encapsulation material of the devices. The interfacial properties, trap properties and dielectric breakdown strength of EMC formulations modified by a type of coupling agent, named AS, were studied. This paper found that the improvement in filler dispersion (i.e. a reduction of filler aggregation rate and an improvement of filler size distribution) and the increase in deep trap depth and density could improve the AC dielectric breakdown strength. The changes in the silica-epoxy interface via the addition of AS can be explained using the Maxwell-Wagner-Sillars (MWS) polarisation mechanism. EMC with 100% AS-treated silica was found to have the best dielectric breakdown performance due to its high dielectric breakdown strength of $21.41\pm 0.20\ \text{kV}/\text{mm}$ measured.